The operation of furnaces, kilns, chemical recovery boilers, etc., depends in part on the temperatures of the processes. Many of these processes take place at such high temperatures that direct visual observation of the process is impossible. Further, the accuracy of direct visual observation, particularly of temperature, is often inadequate for proper process control. Thus, a variety of remote high temperature-monitoring systems have been developed. A main focus of these high temperature-monitoring systems is to provide an indication of the relative or absolute temperature at various locations in the process area. The temperature measurements are then used in the process control system. For example, in a furnace control process, relative variations in the furnace surface temperature can be used as feedback for the control of the discharge and placement of additional fuel.
In prior temperature-monitoring systems, emphasis was placed on the relative temperatures, rather than the absolute temperatures, across the process area. This emphasis was dictated in part by limitations in the temperature-monitoring technology. Often, the temperature-monitoring systems include infrared cameras connected to imaging devices. A video image of the surface is gathered by the camera. The video image is then shaded or colored and displayed. The shading/coloring differences indicate relative temperature differences. Such shaded or colored images provide no absolute temperature information. PG,3
Temperature-monitoring systems have been developed to provide limited absolute temperature measurements in applications that require such information. These systems are generally limited in the amount and accuracy of absolute temperature information that is generated by the system.
One such temperature-monitoring system provides absolute temperature verification for an area of a furnace. The monitoring system includes an infrared camera, a thermocouple or temperature sensor, and an imaging device. The thermocouple is positioned in the furnace in the line of sight of the camera. The position of the thermocouple relative to the furnace surface is referred to as the reference point. In operation, the image gathered by the infrared camera is converted into a colorized video image via a false color display. The video image data is also converted into temperature data using a standard conversion algorithm. The temperature data generated from the video image data must be validated to avoid errors due to improper calibration of the infrared camera. To validate the converted temperature data, the thermocouple temperature reading is compared to the converted temperature data for the reference point. If the converted temperature value is within an acceptable range relative to the thermocouple temperature reading, then the entire set of converted temperature data is accepted; otherwise, the converted temperature data is rejected.
One of the major disadvantages of such a temperature-monitoring system is that the thermocouple and the camera must be accurately aligned, i.e., the reference point must be identifiable in the video image data. If the devices are not properly aligned, the converted temperature data for the reference point may have a low correspondence with the thermocouple measurement and the converted temperature data will be repeatedly rejected. Additionally, if the devices are not properly aligned and the converted temperature value happens to fall in the acceptable range, the entire converted data set will still be accepted. Finally, since a calibration "range" is utilized, the system will be subject to inaccurate temperature readings.
The present invention overcomes these and other problems in the prior art.